Interval timer



Sept. 14,1965

Fi ure 1 Filed June 18, 1962 F. A. MILLER ETAL INTERVAL TIMER :ILOAD 6Sheets-Sheet 1 INVENTORS Frederick A. Miller David E. Earls ept- 1965 F.A. MILLER ETAL 3,206,650

INTERVAL TIMER Filed June 18, 1962 s Sheets-Sheet 2 TTT Fi ure 2 l l 1 IO INVENTORS Frederick A. Miller 8 David E. Earls w 6, w M

F. A.- MILLER ETAL Sept. 14, 1965 INTERVAL TIIER 6 Sheets-Sheet 3 CwN Nvvv Filed June 18. 1962 I INVENTORS Frederick A. Miller David E. EarlsFi ure 4 Sept. 14, 1965 F. A. MILLER ETAL. 3,206,650

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INTERVAL TIMER Filed June 18, 1962 6 Sheets-Sheet 5 INVENTORS FrederickA. Miller David E. Earls If hm fi N mm n v A i N u v tn" Flllllllll 1rOr m FPC m 2% a."

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J L I r s m A N Ill IL j I (5 INVENTORS Frodurlck A. Miller David E.Earls United States Patent 3,206,650 INTERVAL TIMER Frederick A. Miller,Indianapolis, Ind., and David E. Earls, Norwalk, Conn., assignors to P.R. Mallory'& Co., Inc., Indianapolis, Ind., a corporation of DelawareFiled June 18, 1962, Ser. No. 203,232 3 Claims. (CL 317-442.)

This invention relates to electronic timers and in particular to anelectronic timing circuit that provides a pulse output for apredetermined time' interval, which output may be used for controlling arelay, solenoid, or other electro-mechanical or electronic devices.

It is another object of this invention to provide a simple timingcircuit which is stable over wide limits of temperature and inputvoltage.

A further object of this invention is to provide a timing circuit whichis adjustable over a range of milli- 'seconds to minutes.

It is a further object of thisinvention to provide a timing circuitwhich has virtually no stand-by power requirements.

It is a further object of this invention to provide a timing circuitwhich utilizes a neon lamp in conjunction with a photo-resistor in abridge circuit, which provides sufiicient energy for de-energizing a lowcost, general purpose relay.

It is a further object of this invention to provide a timing circuitwhich eliminates the problem of dark effect which effect tends toincrease the breakdown voltage of the neon lamp, thereby affecting thetime interval.

It is a further object of this invention to provide a timing circuitwhich may be practically immediately recycled. It is a further object ofthis invention to provide a timing circuit having all the above featuresat low cost.

Among the improved features disclosed in the present invention are:

(1) A bridge circuit incorporating a relay.

(2) Means for unbalancing the circuit to operate a relay.

(3) Voltage regulating means to stabilize the circuit.

(4) Means to overcome a dark efiect in a neon tube which is triggered tounbalance the bridge circuit incorporating the output relay.

(5) A momentary output switch which is manually operative to start atiming cycle.

FIGURE 1 is an electrical schematic illustrating the basic circuit ofthe present invention.

FIGURE 2 is a modification of FIGURE 1 permitting the reduction of anare that may develop in a lamp and means for completely discharging a,capacitor.

.FIGURE 3 is a modification of the circuit of FIGURE 2 permittingvoltage regulation.

FIGURE 4 is a modification of FIGURE 3 including a bridge circuit havinga photoresistor and a.relay coil and a means to overcome the dark effectof a lamp.

FIGURE 5 is a modification of the circuit of FIGURE I 4 without voltageregulation but including a reset means.

FIGURE 6 is an interval timer including an adjustable time means.

Referring now to the drawings, the basic circuit is shown in schematicFIGURE 1.- A DC. power supply of value E which must be greater than thebreakdown with two important additions.

3,206,650 Patented Sept. 14, 1965 tothe load. Resistor 8 normally wouldnot supply sufficient current to maintain conduction of lamp 12. As aresult lamp 12 will extinguish in a short time, and the cycle willrepeat, except starting from a voltage point on the RC. curvecorresponding to the extinguishing voltage of lamp 12. Thus, if E isheld constant, the pulse rate will be constant except for the firstpulse period, which 'will be longer than the rest.

Improvements to and modification of FIGURE 1 are shown in schematicFIGURE 2. In the circuit of FIG- URE 1 an arc may develop in the lamp 12under certain conditions. Resistor 11 precludes these conditions. Italso reduces the change of characteristics of lamp 12 with use. It alsoallows capacitor 9 to maintain conduction in lamp 12 for longer time,thus producing an output pulse of greater energy. Relay or solenoidcontacts 21, 22 and 23, operated by relay coil 15, allows capacitor 9 todischarge completely through resistor 10, which is used to limit thedischarge current, thus preventing'weldingof contacts 21 and 23. Bycompletely discharging capacitor 9, the pulse rate is kept constant andequal to the otherwise longer first period. Schematic FIGURE 2 alsoshows a DC. power supply consisting of diode 2, filter capacitor 4 andcurrent-limiting resistor 1, which supply allows the pulse timingcircuit to be energized from the AC. mains E through the DC. powersupply. Relay or solenoid coil 15 also operates contacts 24, 25, and 26to obtain a higher-powered output.

Since the time between pulses depends basically upon the resistance ofresistor 8, the capacitance 'of capacitor 9, the breakdown voltage oflamp 12, and the voltage E of the power supply, and since the mentionedvalues of 8, 9, and 12 are essentially constant, the most importantfactor tending to produce varying pulse rates is the voltage ESchematicFIGURE 3 is similar to the preceding circuit except for theaddition of a voltage regulator. The basic network for regulationconsists of resistor 5 in series with two series-connected gas lamps, 6and 7. Lamps 6 and 7 tend to burn at a constant voltage of about 55volts each. Therefore E tends to be a constant volts and any voltagefluctuations of E, are absorbed by the resistor 5. Capacitor 3 is usedto extend the lower limit of input voltage which will initiateconductionhence regulation-by lamps 6 and 7. The following explanationof how this is accomplished may be correct. When E is a positive valuegreater than the breakdown voltage of lamp 7, lamp 7 will conduct for aperiod long enough to cause capacitor 3 to acquire a charge sufficientto cause extinction of lamp 7. This cycle may be repeated as long as Eis increasing in a positive direction. This action will leave point Acharged negatively with respect to E and leave lamp 7 in arecently-conducting state. As E goes increasingly negative from the peakpositive voltage, it will reach the point where the voltage on capacitor4 plus the voltage on capacitor 3 minus the decreasing voltage E willequal the breakdown voltage of lamp 6. The net results are that bothlamps are ignited each shortly after the other, making available ionswhich decrease the breakdown voltage, and the voltage stored oncapacitor 3 is of such polarity as to aid the supply voltage inobtaining breakdown.

Schematic FIGURE 4 is, similar to the foregoing'but One addition is abridge circuit includng the photoresistor l6 and the relay coil. Thepurpose of the bridge is to allow the light pulse from lamp 12 tocontrol the point at which a relay or other device terminates an activetimed cycle instead of merely pulsing this same device.v WithE appliedand after momentarily-closing contacts 18, 19, and 20, a DC. voltage-will be appliedtothe bridge. Since resistors 3 13 and 14 are of equalvalue, the resistor 17 is of much lower value than darkenedphotor'esistor 16, the bridge is highly unbalanced and a holding currentwill pass through coil 15. When lamp 12 flashes, the bridge will bemomentarily balanced and the relay having coil 15 will drop out'endingthe timed interval.

' In the circuit of FIGURE 3 there is a device peculiarity which maygreatly degenerate the accuracy of the timed period. This peculiarity isthe dark effect of the lamp 12 which effect increases the breakdownvoltage of a gas lamp which has been left inoperative in the dark for aperiod of time. To eliminate or greatly reduce this efiect a smallcapacitor 27 is placed in the circuit in such a manner that it willbecome charged to peak line voltage when the circuit is not in a timingcycle. Upon closing contacts 18 and 20 this charged capacitor is placedacross lamp 12 very briefly igniting it thereby allowing only the timedinterval for lamp 12 to acquire a dark effect.

Schematic FIGURE shows a similar interval timer but without voltageregulation but including a set of contacts 29 and 30 which are normallyopen during the timed interval and which may be momentarily closedduring the timed interval to reset the timer to the start of theinterval. The contacts merely connect the low-valued resisor across thetiming capacitor 9.

Schematic FIGURE 6 shows an interval timer having some of theaforementioned features and having an adjustable voltage divider withwhich an adjustable inter-- val may be had. Practical considerationsinclude a limit on adjustable divider 31 to insure that the voltageavailable to the timing network will always exceed the breakdown voltageof lamp 12.

There are numerous modifications and changes that may be made in thepresent invention without departing from the scope thereof. We do notintend to be limited to the exact details shown and described, but onlyinsofar as defined by the scope and spirit of the appended claims.

What is claimed is:

1. An electrical timing circuit comprising: a'triggering circuitincluding a normally disabled gas diode, a time constant networkincluding a resistor and capacitor, said capacitor being connected inparallel with said gas diode, a direct current power supply feeding saidtime constant network with 'suflicien-t voltage to cause said gas diodeto fire after a predetermined time interval, alight sensitive detectorcoupled to said gas diode to provide a higher powered output, said lightsensitive detector connected as one leg of an electrical bridge, saidbridge comprising resistances for the other three legs, a coil of an.electromechanical device connected between opposite pairs of legs ofsaid bridge, means .for momentarily switching a low impedance acrossthat leg of said bridge which is adjacent to said light sensitivedetective leg which said two legs form a circuit parallel to said coil,said switching means causing a bridge imbalance 'sufiicient to causesaid coil to be fully energized when a direct current voltage ofsuitable value is impressed upon said bridge, said legs and said voltagebeing of such value so .as to provide holding current for said coil whensaid light sensitive detector is not illuminated and to provide noholding current or a small value of reverse current when said lightsensitive detector is illuminated, second switching means formomentarily connecting said power supply to said circuit, a thirdswitching means for connecting said power supply to said circuitwhenever said coil is sufficiently energized.

2. The circuit of claim 1, wherein a fourth switching .means connectsone side of said first capacitor through References Cited by theExaminer UNITED STATES PATENTS 2,867,754 1/59 OBleness 317-142 2,999,2089/61 Ruehlemann.

3,107,320 10/63 Brittain et a1. 317148.5 3,136,926 6/64 Smith 3l7142 XROTHER REFERENCES- Electronics at Work in the Home, Service Dept., TheMaytag Co., 1960.

SAMUEL BERNSTEIN, Primary Examiner.

MAX L. LEVY, Examiner.

1. AN ELECTRICAL TIMING CIRCUIT COMPRISING: A TRIGGERING CIRCUITINCLUDING A NORMALLY DISABLED GAS DIODE, A TIME CONSTANT NETWORKINCLUDING A RESISTOR AND CAPACITOR, SAID CAPACITOR BEING CONNECTED INPARALLEL WITH SID GAS DIODE, A DIRECT CURRENT POWER SUPPLY FEEDING SAIDTIME CONSTANT NETWORK WITH SUFFICIENT VOLTAGE AS CAUSE SAID GAS DIODE TOFIRE ATER A PREDETERMINED TIME INTERVAL, A LIGHT SENSITIVE DETECTORCOUPLED TO SAID DIODE TO PROVIDE A HIGHER POWERED OUTPUT, SAID LIGHTSENSITIVE DETECTOR CONNECTED AS ONE LEG OF AN ELECTRICAL BRIDGE, SAIDBRIDGE COMPRISING RESISTANCES FOR THE OTHER THREE LEGS, A COIL OF ANELECTROMECHANICAL DEVICE CONNECTED BETWEEN OPPOSITE PAIRS OF LEGS OFSAID BRIDGE, MEANS FOR MOMENTARILY SWITCHING A LOW IMPEDANCE ACROSS THATLEG OF SAID BRIDGE WHICH IS ADJACENT TO SAID LIGHT SENSITIVE DETECTIVELEG WHICH SAID TWO LEGS FORM A CIRCUIT PARALLEL TO SAID COIL, SAIDSWITCHING MEANS CAUSING A BRIDGE IMBALANCE SUFFICIENT TO CAUSE SAID COILTO BE FULLY ENERGIZED WHEN A DIRECT CURRENT VOLTAGE OF SUITABLE VALUE ISIMPRESSED UPON SAID BRIDGE, SAID LEGS AND SAID VOLTAGE BEING OF SUCHVALUE SO AS TO PROVIDE HOLDING CURRENT FOR SAID COIL WHEN SAID LIGHTSENSITIVE DETECTOR IS NOT ILLUMINATED AND TO PROVIDE NO HOLDING CURRENTOR A SMALL VALUE OF REVERSE CURRENT WHEN SAID LIGHT SENSITIVE DETECTORIS ILLUMINATED, SECOND SWITCHING MEANS FOR MOMENTARILY CONNECTING SAIDPOWER SUPPLY TO SAID CIRCUIT, A THIRD SWITCHING MEANS FOR CONNECTINGSAID POWER SUPPLY TO SAID CIRCUIT WHENERVER SAID COIL IS SUFFICIENTLYENERGIZED.